Done byR.Krishna

What are cells?

•Cell: a cell is a basic unit of structure and function of life. In other words, cells make up living things and carry out activities that keep a living thing alive. We can find cells almost anywhere on earth e.g.:- In the air, inside us, plants e.t.c

Continued

•What makes a cell?•A cell is a living thing.•Cells are able to make more cells like

themselves.•New cells can only come from existing

cells (cells that are already existing).

Oh yeah! Some HISTORY for you•I am sure you are all asking yourselves,

“Who was the first person to look at cells.” Well thanks for asking! I will tell you.

•In the 1665 there was a man named Robert Hooke. Robert lived in Britain and was a scientist. He was the first person to observe cells.

•Robert took a piece bark from an old oak tree and looked at it through a microscope.

Robert Hooke

Microscope used by Robert Hooke

Modern day microscope

History Continued•The bark looked like it was made up of

many small rooms (kind of like a house with many bedrooms). He named the rooms, or structures, he saw under the microscope cells.

•This is how the word cells came to be!! Exciting stuff isn’t it!!

Cork cells under microscope

History Continued•After the discovery of cell by hooke other

people made discoveries about cells. Some of them are :-

•Antony van Leeuwenhoek discovered the first living cell(remember the cells that hooke saw were dead ones )by inventing a special microscope in 1674.

•Matthias Jakob Schleiden discovered cell wall in plant cell in 1838.

History Continued(getting bored! Don’t worry this the last slide of history)•In 1839 Theodore Schwann observed cell

membrane in an animal cell.•Robert brown discovered nucleus in 1831•Purkinje discovered protoplasm in 1839•Rudolph Virchow stated that all cells are

formed from pre-existing cells.•Watson and crick discovered DNA.•Schleiden and Schwann proposed the “

CELL THEORY ” (what’s that ? Have patience !)

The cell theory

•All organisms are made of one or more cells

•The cell is the basic unit of all living things

•All cells come from pre-existing cells

Organelles of Cells and their Basic Functions

• Mitochondria • It has double membrane organelle central cavity is filled with matrix • inner membrane folds known as cristae • large surface area for chemical reactions of cellular

respiration • Functions- • generation of ATP • “powerhouse of cell” • Mitochondria self-replicate increases with need for ATP• They have circular DNA with 37 genes only inherited from mother

Cross-section of a mitochondria

Continued

Now what is ATP?ATP(adenosine triphosphate) is the source of energy for the cells to perform its functions

• Nucleus: The nucleus is a structure usually located near the center of the cell. It controls the activities of the cell. The nucleus is a home to the cell’s chromosomes. What are chromosomes you ask?

Continued •Chromosomes: They are genetic structures that contain

information to make new cells. Basically, the instructions for how to make new cells. They contain DNA responsible for hereditary characters of the cell.

•Nucleolus: This structure is found inside the nucleus. It is responsible for making ribosomes. We will get to this term in a bit. Thanks for your patience!

Nucleolus inside a nucleus

ContinuedNuclear membrane: This surrounds and protects the nucleus. The nucleus has its own protector. This membrane is double-layered.

Continued • Plastids- they are of 3 kinds-• 1.chloroplast-helps to make food for the

plant by photosynthesis.• 2.chromoplast-gives colour to the some

parts of plants like flowers

• 3.leucoplasts-store food

• Glyoxysome-breakdown of fatty acids to sugars

• Ribosomes -Ribosome turns RNA (Ribonucleic acid) into protein. The ribosome is basically the storage space for energy. in other words it releases and holds in energy for the cell. They are the structural support, and the catalyst for protein synthesis. :)he

Continued •Endoplasmic Reticulum-Say it with me “En-

do-plas-mic ri-tic-eww-lum.” •Now say it 5 times fast….no just kidding! • it is made up of 2 parts -•1. SER(smooth endoplasmic reticulum)-it

helps in lipid synthesis.•2. RER(rough endoplasmic reticulum)- it

helps in protein synthesis and sends them to different parts of the cell. It is rough because it has ribosomes attached to its surface.

•Golgi Apparatus-delivery system for the cell and also helps in manufacturing of lysosomes.

continued• Lysosomes-• They are Membranous vesicles and formed in Golgi

complex • They are filled with digestive enzymes and pump in

H+ ions until internal pH reaches 5.0 • Functions -• digest foreign substances • autophagy (recycles own organelles) • Autolysis(Lysosomal digestion of the cell after death)

• Vacuoles-These are fluid-filled structures used to store different substances and help in osmo-regulation. In animal cells there are often many small vacuoles. Plants have large vacuoles.

A vacuole

Continued

•Peroxysomes-help in performing oxidative reactions in a cell.

•Centriole- helps in cell division by forming a milotic spindle also know as spindle fiber apparatus. In plants polar caps do the same function.

Continued •Plasma membrane: The plasma

membrane surrounds the cell. It regulates the movement of substances in or out of the cell. It is made up of a lipid and protein bi-layer. Think of the membrane as a gatekeeper, it only allows some materials to pass through, but keeps others out.

•Cytoplasm: This is a gel-like fluid, that takes up most of the space inside a cell. Cytoplasm kind of looks like jelly.

Types of cells

•Prokaryotic cells- •E.g.:-Bacteria•Eukaryotic cells-•Unicellular•E.g.:-Protists•Multi-cellular•E.g.:-Fungi, Plants, Animals

Prokaryotic cells- •Prokaryotes – the meaning of their name

is pro-primitive karyon-nucleus. •They are small in size and they don’t have

a properly arranged nucleus.•They have single chromosome.•Nucleolus is also absent.•Generally they are pathogens.•They have circular or coiled DNA

A prokaryotic cell

Bacteria•Characteristics•Greek for “small stick”•Most Abundant organism•Found in all Media• Many are Pathogens• Move by Flagella or by Gliding• Asexual Reproduction• Beneficial in Everyday Needs

Bacterial cells Escherichia coli cells

Eukaryotic cell

•Eukaryotes – the meaning of their name is eu- developed karyon-nucleus.

• It has membrane bound nucleus.•It contains many organelles.•It has linear DNA.•Membrane bound organelles are present.•They have more than 1 chromosome.

Eukaryotic Cell

Protists•Protozoa•They are animal like and Motile•Feed by Phagocytosis (what's

that! Wait for the next slide)

•Algae•Plant like•Uses photosynthesis for its

nutrients•Some motile, some are not

Phago and pinocytosis

•Phagocytosis is the ingestion or eating of large particles by living cells

•Pinocytosis is the intake of fluid by the cell also known as cell-drinking.

Fungi

•Characteristics•All come from a common•Thought to be more related to animals

than plants•Most are symbiotic•Lacks organs•Reproduce sexually or asexually•Many are used in everyday human life

Fly Agaric fungi Yeast cells

The Plant Cell•Characteristics•Has a cell wall made of cellulose•Has a large central vacuole•Undergoes photosynthesis •Contains Chloroplasts which contain

Chlorophyll•The cells differentiate in to dermal tissue,

vascular tissue, or ground tissue

The three main structures for a plant cell

•Cell Wall : This wall provides extra support for the cell and gives it a shape. In other words, if there was no cell wall then the cell would have no shape.

•Chloroplasts : These make food for the plant. They are green.

•Chlorophyll : This is very important in making the food for the plant. This structure takes in sunlight and makes sugar for the plant to eat and become green.

Cell wall in plant cell

Chloroplast

Plant cells

Example of Whole Plants

The Animal Cell•Animals are made up of many different

types of cells. The structures I am about to tell you about are found in a typical animal cells.

•Please note: Not all animal cells contain all the same structures.

•Thank you for noting!

Continued

•Characteristics•Unicellular and Multicellular•Lack a cell wall and chloroplasts.•They have small vacuoles•Appear spherical in shape•Contains a variety of organelles •They cannot produce their own food.

The Exception: Viruses•Characteristics•Latin for “poison”•Does not meet all the criteria of “Life” •Not made up of cells•Contains DNA or RNA, but not usually both•Require a host to replicate•Causes the common cold, the flu,

chickenpox, AIDS, bird flu etc.•Some uses e.g. –bacteriophage used to kill

bacteria

Structure of a virus

Bacteriophage virus attacking a bacterial cell

H1N1 virus (influenza)

The End!!•Thank you for your cooperation and

attention!!•Hope you learned some new, exciting

things.•Good luck people!

•Regards•Krishna.R